Proton AA-1150 Woes

[Lazarus Short]

I suppose what I'm facing with this amp is simply on the order of "Do this every few years, or at least check it." I bought this amp really cheap at a local audio meet, and asked no questions. Lately, I kept hearing static-like noise from time to time...and it was only getting worse. A preamp change did not change the noise. I pulled pre and power amps out of the system - just now had a look at the Proton's innards, being VERY familiar with the Cyrus 2's innards, and fairly confident it was not the source of the noise.

I eyeballed everything with a good flashlight. I wiggled one known source of trouble - the signal inputs, which are soldered to the main board. Yup, one was loose, but I can re-flow the solder. Then I saw more. Worse, it looks like someone had been in there ahead of me and used WAY too much heatsink compound. Do you agree?

So, I have three concerns:

1. A number of semi-bad to bad solder joints, easily solved.

2. There is some corrosion on some joints - is this a problem?

3. If there is (photo following) too much heatsink compound on the outputs, should I go ahead, clean and apply new? The white stuff looks a bit dry, and is even cracked in places. If I do clean and replace, I plan to use silicone.

 

[overmodulated]

Definitely way too much thermal paste, I'm not an authority in that but I believe it can actually hinder heat transfer to the heat sink. Just like the commercial on TV would say years ago… Just a little dab will do ya.

I have Wilson audio speakers and they use the dreaded resistors to protect the drivers, which isn't necessarily a bad idea but mine are hidden inside of a hatch is on the bottom of the speakers. It wouldn't be bad with your normal speaker, but these beast are 230 pounds apiece, and every time I blew a resistor which was getting a little frequent because I like to turn the volume up I had to flip the speaker over, or lay it on its side and replace the resistors. There's four of them but only to have given me trouble.

I bought some resistors from Mouser, and I was told that a little bit of difference in specs was going to be in inaudible and it was, and evidently Wilson had some proprietary resistors made. Anyway I drilled some holes in the hatch, and ran the mid range and tweeter resistors outboard using some good thermal paste on a better heat sink with a couple little fans… end of story never overheated again. It was really surprising and how hot does resistors came when I started the pump 100 W or more through the speakers, actually burn your finger.

Anyway if that's going to heat sink, not that you don't know what you're doing but I would use some good thermal paste and just put a little dab on there I think the kind I used is noctura available on Amazon, I hope that's the right spelling but they also make computer fans.

 

[laatsch55]

I've melted the solder in my crossovers on the K's...

 

[Vintage 700b]

I've melted the solder in my crossovers on the K's...

Had to be cranking Shpongle .

 

[overmodulated]

Had to be cranking Shpongle .

you wouldn't think that they would get that hot but they do. I've gotten resistors to blow/melt apart in my Wilsons cranking them for too long. although mine are 22 years old, they were not cheap even back in the day, you would think they would put them on a better heat sink.

 

[e30m3mon]

Reminds me of a party I used the 400-II for, many years ago. A pair of large Bose speakers attached to it…you could see down the duct port that the crossovers were glowing orange! The amp survived

 

[overmodulated]

Quick break in that way

 

[laatsch55]

Had to be cranking Shpongle .

Indeed-----" God Particle"

 

[Lazarus Short]

I had the time today, so I cleaned the transistors first, using a small screwdriver to start, and after that, Q-Tips, tissues and pipe cleaners. Then, on to re-flowing a few solder joints, most importantly one of the input jacks. Then, I pulled the covers off the speaker relays, made sure they operated correctly and cleaned the contacts with 220-grit sandpaper soaked in DeOxit - just a few swipes.

Now, everything works and sounds right...right away, not after half a minute, and the static-like noise is gone.

SUCCESS!!

Thanks to all for advice and help!

 

[overmodulated]

I had the time today, so I cleaned the transistors first, using a small screwdriver to start, and after that, Q-Tips, tissues and pipe cleaners. Then, on to re-flowing a few solder joints, most importantly one of the input jacks. Then, I pulled the covers off the speaker relays, made sure they operated correctly and cleaned the contacts with 220-grit sandpaper soaked in DeOxit - just a few swipes.

Now, everything works and sounds right...right away, not after half a minute, and the static-like noise is gone.

SUCCESS!!

Thanks to all for advice and help!

View attachment 73565

congrats!